1. Field of the Invention
The present invention relates to an X-ray generator to be used for an X-ray inspection device for industrial or medical use or for any of various types of X-ray spectrometers and measurement devices using the diffraction or refraction of X-rays, and in particular, to a transmission type X-ray generator where X-rays are generated by colliding electrons with a target inside a vacuum chamber and are emitted to the outside of the chamber mainly in the direction in which the electrons travel.
2. Description of Related Art
X-ray generators of the type for generating X-rays by colliding electrons with a target inside a vacuum chamber include those using a reflective type target from which X-rays are taken out in a direction that is different from the direction in which the electrons travel and those using a transmission type target from which X-rays are taken out in approximately the same direction in which the electrons travel. Transmission type targets are usually formed of a thin film, and therefore, have a shorter life span as compared to reflective type targets that can be made of a bulk material. In order to make the life span of the transmission type targets longer, various ways and means have been figured out so that a number of points for generating X-rays can be set in the target plane, that is to say, the point that is irradiated with an electron beam can be changed on the target.
As shown in FIG. 4, an open type X-ray generator using a transmission type target contains a so-called electron gun 402 having an electron source and a group of electrodes within a vacuum chamber 401, and is formed so that the inside of the vacuum chamber 401 can be vacuumed at any time by means of a vacuum pump 403. An X-ray emitting window 404 that is formed so as to integrate a target is air-tightly supported by the vacuum chamber 401 using an O-ring 405 that is located eccentrically with respect to the trajectory of the electron beam B from the electron gun 402. When the X-ray emitting window 404 is rotated in this structure, a number of points for generating X-rays can be set relatively easily in the target plane.
In contrast, as shown in FIG. 5, in a sealed type, an X-ray emitting window 504 that is formed so as to integrate a target is air-tightly fixed to a vacuum chamber 501 through welding or brazing, and therefore, cannot be rotated unlike the described above type. In this sealed type structure, the point on the target that is irradiated with the electron beam B from the electron gun 502 cannot be changed, and therefore, the following measures have been proposed.
One measure is to provide a permanent magnet that is movable along the periphery outside the vacuum chamber so that the magnetic field created within the vacuum chamber by the permanent magnet can be changed when the location of the permanent magnet is changed. In accordance with this technology, the trajectory of the electron beam can be changed so that the point irradiated with the electron beam can be changed on the target (see Patent Document 1).
Another measure is to provide a vacuum chamber with such a structure that a main body portion to which an electron gun is fixed and a target support portion to which an X-ray emitting window that is integrated with a target is fixed are formed of different members and these are linked through a linking body so as to be displaceable relative to each other. In accordance with this technology, the target support portion can be inclined to any direction relative to the trajectory of the electron beam from the electron gun so that the point irradiated with the electron beam can be changed on the target (see Patent Document 2).